<template>
  <transition
      @before-enter="beforeEnter"
      @enter="enter"
      @after-enter="afterEnter"
      @before-leave="beforeLeave"
      @leave="leave"
      @after-leave="afterLeave">
    <slot></slot>
  </transition>
</template>

<script>
export default {
  name: "z-spread",
  props: {
    duration: {
      type: [Number, String],
      default: '500'
    }
  },
  data() {
    return {}
  },
  computed: {
    elTransition() {
      return `${this.duration}ms height ease-in-out, ${this.duration}ms padding-top ease-in-out, ${this.duration}ms padding-bottom ease-in-out`
    }
  },
  methods: {
    beforeEnter(el) {
      el.style.transition = this.elTransition
      if (!el.dataset) el.dataset = {}

      el.dataset.oldPaddingTop = el.style.paddingTop
      el.dataset.oldPaddingBottom = el.style.paddingBottom

      el.style.height = 0
      el.style.paddingTop = 0
      el.style.paddingBottom = 0
    },
    enter(el) {
      el.dataset.oldOverflow = el.style.overflow
      if (el.scrollHeight !== 0) {
        el.style.height = el.scrollHeight + 'px'
        el.style.paddingTop = el.dataset.oldPaddingTop
        el.style.paddingBottom = el.dataset.oldPaddingBottom
      } else {
        el.style.height = ''
        el.style.paddingTop = el.dataset.oldPaddingTop
        el.style.paddingBottom = el.dataset.oldPaddingBottom
      }

      el.style.overflow = 'hidden'
    },
    afterEnter(el) {
      el.style.transition = ''
      el.style.height = ''
      el.style.overflow = el.dataset.oldOverflow
    },
    beforeLeave(el) {
      if (!el.dataset) el.dataset = {}
      el.dataset.oldPaddingTop = el.style.paddingTop
      el.dataset.oldPaddingBottom = el.style.paddingBottom
      el.dataset.oldOverflow = el.style.overflow

      // el.style.height = el.scrollHeight + 'px'
      el.style.height = window.getComputedStyle(el).height
      el.style.overflow = 'hidden'
    },
    leave(el) {
      if (el.scrollHeight !== 0) {
        el.offsetHeight
        el.style.transition = this.elTransition
        el.style.height = 0
        el.style.paddingTop = 0
        el.style.paddingBottom = 0
      }
    },
    afterLeave(el) {
      el.style.transition = ''
      el.style.height = ''
      el.style.overflow = el.dataset.oldOverflow
      el.style.paddingTop = el.dataset.oldPaddingTop
      el.style.paddingBottom = el.dataset.oldPaddingBottom
    }
  },
}
</script>

<style lang="scss" scoped>
</style>
